Over the next six months, the XXI Bomber Command under LeMay firebombed 67 Japanese cities. The firebombing of Tokyo , codenamed Operation Meetinghouse , on March 9–10 killed an estimated 100,000 people and destroyed 16 square miles (41 km 2 ) of the city and 267,000 buildings in a single night. It was the deadliest bombing raid of the war, at a cost of 20 B-29s shot down by flak and fighters.  By May, 75% of bombs dropped were incendiaries designed to burn down Japan's "paper cities". By mid-June, Japan's six largest cities had been devastated.  The end of the fighting on Okinawa that month provided airfields even closer to the Japanese mainland, allowing the bombing campaign to be further escalated. Aircraft flying from Allied aircraft carriers and the Ryukyu Islands also regularly struck targets in Japan during 1945 in preparation for Operation Downfall.  Firebombing switched to smaller cities, with populations ranging from 60,000 to 350,000. According to Yuki Tanaka , the . fire-bombed over a hundred Japanese towns and cities.  These raids were also devastating. 
Instead [of allowing other options to end the war, such as letting the Soviets attack Japan with ground forces], the United States rushed to use two atomic bombs at almost exactly the time that an August 8 Soviet attack had originally been scheduled: Hiroshima on August 6 and Nagasaki on August 9. The timing itself has obviously raised questions among many historians. The available evidence, though not conclusive, strongly suggests that the atomic bombs may well have been used in part because American leaders “preferred”—as Pulitzer Prize–winning historian Martin Sherwin has put it—to end the war with the bombs rather than the Soviet attack. Impressing the Soviets during the early diplomatic sparring that ultimately became the Cold War also appears likely to have been a significant factor.